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A291765
Compound filter (sum of proper divisors & prime signature): a(n) = P(A001065(n), A046523(n)), where P(n,k) is sequence A000027 used as a pairing function.
3
0, 2, 2, 18, 2, 61, 2, 98, 25, 86, 2, 367, 2, 115, 100, 450, 2, 517, 2, 550, 131, 185, 2, 1747, 42, 226, 203, 769, 2, 2527, 2, 1922, 205, 320, 166, 4060, 2, 373, 248, 2678, 2, 3457, 2, 1315, 979, 491, 2, 7579, 63, 1474, 346, 1642, 2, 3982, 248, 3805, 401, 698, 2, 13969, 2, 775, 1367, 7938, 295, 5749, 2, 2404, 523, 5327, 2, 18844, 2, 1030, 1819, 2839, 295
OFFSET
1,2
LINKS
FORMULA
a(n) = (1/2)*(2 + ((A001065(n)+A046523(n))^2) - A001065(n) - 3*A046523(n)).
PROG
(PARI)
A001065(n) = (sigma(n)-n);
A046523(n) = { my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]); }; \\ This function from Charles R Greathouse IV, Aug 17 2011
A291765(n) = (1/2)*(2 + ((A001065(n)+A046523(n))^2) - A001065(n) - 3*A046523(n));
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Sep 10 2017
STATUS
approved